1. Technical Field
The invention relates to an electrode for influencing ion motion in mass spectrometers, having a dielectric substrate and a conducting layer on portions of the substrate, wherein peripheral borders, edges or convex shapes of the conducting layer adjoin free regions of the substrate. “Free regions” are such regions which are not covered by the conducting layer. The layers are relatively thin, of the order of micrometers. Borders, edges or convex shapes are typically hardly visible or invisible elevations relative to the surface of the substrate.
The invention particularly relates to electrodes for ion-optical elements in mass spectrometers, preferably combined with a high DC voltage or a radiofrequency high voltage. A preferred application of the invention relates to electrodes with a metallic coating on an insulating substrate.
2. Related Art
Termination electrodes which are formed from a ceramic plate as a substrate in combination with a metallic coating may be provided in curved radiofrequency ion traps. The metallic coating is only applied to the substrate in regions, specifically in a region which is “visible” to the ions. Electrical discharges can be observed in the region of the peripheral edges of the electrically conducting, metallic coating. It is even possible for whiskers to be formed over time in the vicinity of the peripheral edges. This increases the risk of an electrical flashover or breakdown still further.
Electrical discharges can occur under all vacuum conditions, even in RF ion traps for ion storage or cooling. The distances of the voltage-carrying parts to each other are important for avoiding electrical charges. Although said distances can be altered, this is always associated with undesired changes in the electric field geometry.
U.S. Pat. No. 6,316,768 B1 describes the use of printed circuit boards (PCBs) in mass spectrometers. Here, the PCBs can also have electrodes suitable for ion transport.